In German-occupied Poland during the darkest days of World War II, a zookeeper and his wife managed to save the lives of hundreds of Jewish people, many of them detained earlier in the Warsaw Ghetto, by providing shelter and refuge for them on the zoo grounds. This extraordinary true story is dramatized in director Niki Caro’s “The Zookeeper’s Wife,” based on the nonfiction book by the naturalist-writer Diane Ackerman.

Caro, who directed “Whale Rider” and “McFarland, USA,” imbues the production with a glossy sheen that, in the trailers and advertisements, might make the film look slight. For WWII films, audiences have learned to be suspicious of those that look too pretty — which, in the case of “The Zookeeper’s Wife,” might make them think it will have a suffocating sentimentality, emotional blackmail and too-neat resolution.

In the film’s romanticized beginning, our heroine Antonina Zabinski (Jessica Chastain, affecting an accent that you’ll probably get used to) does seem to live the most picture-perfect life ever — frolicking with the free-roaming zoo animals, sipping tea on her balcony and gazing lovingly at her doting husband and son. But as the film moves on, Caro keeps the action and emotion grounded and real throughout.

The director chooses silences and understatement, since this inherently amazing story doesn’t need dressing up. It just needs to be told. And the initial setting of the stage is necessary, too, not just to introduce the characters, but to set up what will become a personal conflict that serves as a microcosm for the war itself: The Zabinskis’ friendship with a German zoologist named Lutz Heck (Daniel Brühl) turns problematic once the Germans invade Poland.

Chastain’s Antonina is ethereal, motherly and tenacious. Though she’s the zookeeper’s spouse, she has just as much, if not more, of a command over the place as her milquetoast husband, Jan. In fact, she treats the zoo animals as she would her own children.

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When an elephant’s baby is in distress and near death, Antonina rushes to their aid, calling each by name and telling the mother elephant that everything will be OK once she frees the baby’s airway. But don’t worry, there’s no sign that the elephants respond to their names, as they might in a Disney flick, but of a fundamental comfort that is palpable between the human and animal.

By the time the zoo is bombed and destroyed by the Nazis, we feel the loss of something that was once good and pure. It’s distressing to see the occupying soldiers shooting animals — whether out of fear, wartime necessity or just plain evil. But it’s also a reminder that humans are not the only ones who suffer during wartime. The script is a little too on-the-nose when Antonina overexplains her fondness for the creatures: “You can see exactly what’s in their hearts.”

Johan Heldenbergh plays Jan Zabinski. (Anne Marie Fox/Focus Features)

But the real power of this story is in what Antonina and her husband (Johan Heldenbergh) do for the persecuted Jews — risking their own lives to stage elaborately planned rescues from the ghetto and providing refuge in their own home for those they’ve saved.

An already tense situation is made even worse when Heck, now Hitler’s chief zoologist, takes a special interest in the zoo — and Antonina. His constant presence threatens to derail the entire rescue operation and causes strife in Antonina’s marriage when Jan’s jealousy gets the best of him. These scenes might easily have been just a tawdry sideshow, but Chastain and Brühl make them captivating.